A high-definition multimedia interface (HDMI) refers to a multimedia interface for transferring uncompressed digital video and audio signals to one cable simultaneously.
An electronic device may continuously check several variables, such as high-bandwidth digital content protection (HDCP) state information in order to increase security for DRM content when playing back DRM content using the HDMI. For example, when a HDCP fail is detected based on the HDCP state information, the electronic device suspends decoding or decryption of the DRM content and cuts off output of digital video and audio signals for the DRM content.
Therefore, the electronic device needs a method for protecting variables from security attack in order to increase security for DRM content. Furthermore, when a HDCP module for generating HDCP is separate from a DRM module for controlling DRM services, the HDCP state information is exposed to the outside when being transmitted from the HDCP module to the DRM module, causing vulnerability to a security attack. Therefore, there is a need for a method for protecting HDCP state information, transmitted from the HDCP module to the DRM module, from a security attack in electronic devices.